Magnetic instabilities in superconducting composites

The development of magnetic instabilities in multifilamentary superconducting composites is analyzed through a study of the thermal and Maxwell equations describing the perturbations of temperature and electric field associated with the flux-jumping phenomenon. Consideration of cases in which a sufficiently large number of superconducting filaments and a sufficiently high current are involved permits treatment of the composite as a quasi-continuous medium. Stability criteria are derived for arbitrary values of the external heat transfer coefficient; it is demonstrated that the stability of the composite depends to a much greater extent on the heat exchange intensity than on heat capacity or the value of the transport current. A simplified calculation scheme is employed to investigate the stability of a circular composite conductor.